A substance immunoreactive to antibodies directed against bovine neuro
tensin (NT) was localized in neurons in the supraesophageal ganglion (
SEG) and optic lobes of larval and adult Locusta migratoria L. Two lar
ge somata were located in the caudal cortex, ventral to the calyces an
d symmetrical to the median of the SEG. Four smaller somata also in th
e caudal cortex were located as two symmetrical pairs at the level of
the central body. These somata formed a diffuse network of varicose fi
bers from the superior lateral to the ventro-lateral protocerebrum bet
ween the pedunculi and frontal cortical region. Some fibers crossed th
e median to the contralateral sides of the SEG. Another pair of immuno
reactive somata whose terminating processes remained unclear was found
at the level of the antennal lobes. Intrinsic networks of fibers were
labeled in the accessory medulla and in layer 4/5 of the medulla. The
se fibers originated from 8-10 small somata near the dorso-frontal rim
of the medulla. All larval stages contained these NT-like immunoreact
ive structures. Results from isoelectric focusing and press-blot analy
sis of SEG homogenates, synthetic neurotensin and neurotensin fragment
s indicate that this substance is similar to bovine neurotensin(1-13).